Soil vapor extraction is employed for sub-surface soil and ground water remediation in locations that have been contaminated, for example with volatile organic compound contaminants. Soil remediation is often required to remove contamination from soils and ground water where underground gasoline storage tanks have leaked. Typically, remediation is performed by extracting soil vapors through one or more extraction wells that have been drilled and screened in the unsaturated soils (vadose zone). The extracted soil vapors are then treated in a thermal oxidization apparatus, which may be a gas flame burner or a gas or electrically heated catalytic oxidizer, whose products are released. Alternatively, the extracted soil vapors may be treated with a carbon adsorber, requiring the carbon material to be regenerated on-site or off-site or replaced periodically. One problem with the approach using the thermal oxidation apparatus is that the oxidation gas products must be released into the atmosphere to avoid further treatment and expense, and the release must be limited to conform with legal or regulatory requirements. Recent developments indicate that any release, particularly of carbon dioxide components of the oxidation gas products, may eventually be prohibited or limited to such an extent that this process may become unfeasible. One problem with the approach using a carbon adsorber is that periodic regeneration or replacement of the carbon adsorber can be prohibitively expensive for remediation sites having high volatile organic compound concentrations in the extracted soil vapors.
Another technique for remediation is to inject oxygen gas into the ground water through a sparging well, in order to enhance the population of beneficial bacteria for biodegradation of the volatile organic compounds contaminating the ground water or soil. One problem with this approach is that injection of oxygen or any gas increases the pressure in the soil, and at high flow rates can lead to escape of fugitive gases through the soil surface into the atmosphere.
There is a need for a soil and ground water remediation process that does not suffer from any of the problems or disadvantages noted above. For example, there is a need for a soil remediation process that prevents escape of fugitive gases through the soil surface. There is a need for a soil remediation process that does not generate undesirable products, such as oxidation gas products. There is a need for a soil remediation process that does not require replacement or chemical/thermal regeneration of an adsorber material such as a carbon adsorber.